sideromelane
A basaltic glass often found in palagonite tuff.
The Korite is a hydrous labradorite; it is in dull brown grains, and is associated with Sideromelane, which has the same composition excepting the absence of water.
Where it comes from
Borrowed from German Sideromelane, coined by Wolfgang Sartorius von Waltershausen in 1853.
Adapted from the Wiktionary entry sideromelane (CC BY-SA 4.0).